ChemInform Abstract: Reaction of Ethylmagnesium Bromide with Carboxylic Esters in the Presence of Titanium Tetraisopropylate.

Abstract

ChemInform Abstract In the presence of equimolar amounts of Ti(OiPr)4 the reaction between the carboxylic esters (I) and EtMgBr (II) affords the 1-substituted cyclopropanols (III) in high yields. This reaction offers a convenient access to cyclopropanols. The mechanism is, so far, not clear.

Efficient Synthesis of Cyclopropane‐Fused Heterocycles with Bromoethylsulfonium Salt

“…[9] Numerous methods have been developed for the construction of azabicyclo[3.1.0]hexanes. [10] These include the Kulinkovich/de Meijere reaction [11,12] , cyclisation of tethered amines with metals (Pd [13] , Ru [14] , Rh [15] , Ag [16] ), cyclisation of tethered cyclopropanes [17] , and the Simmons-Smith [18] /CoreyChaykovsky [19] /sulfur ylide-Au [20] cyclopropanations. These methods are usually only effective in the synthesis of one specific type of scaffold.…”

Preparation of 3-bromomethyl-3-butenal diethylacetal and its conversion into isoprenoid aldehydes derivatives

“…Inasmuch as an efficient procedure for the conversion of a mixture of cis-and trans-retinals VIb into a pure trans-isomer was published [7], we did not attempt to improve the stereoselectivity of its formation from compound Vb. The hydrolysis of cyclic acetals VIIa, VIIc-VIIe without dehydration and the shift of the multiple bond cleanly occurred in aqueous (1) EtMgBr _ Ti(OPr-i) 4 (2) MsCl _ Et 3 N Mg + BrCH 2 BrCH 2 +Et 2 O Scheme 1.…”

“…The use of this compound as a nucleophilic C 5 -isoprenoid building block made it possible to obtain the corresponding esters both with the methylene-and the methyl-substituted carbon skeleton [1][2][3]. In this study an analogous approach was extended to the preparation of 3-bromomethyl-3-butenal diethylacetal (I) by the cyclopropanation of an available ethyl 3,3-diethoxypropionate (II) with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide [4,5] followed by subsequent mesylation and by the treatment of obtained mesylate III with magnesium bromide in anhydrous ethyl ether [1,6] (Scheme 1).…”

Synthesis of epothilones molecule fragment (15R)-C 13 -C 21 from D-mannitol

“…In the course of the development of cyclopropanol procedures for the syntheses of naturally existing biologically active compounds [7][8][9] we found effi cient ways to the synthesis of compound (S)-(III) from L-malic acid [10], and compounds (S)-(IV) and (R)-(IV), from methyl 2,3-O-isopropylidene-D-glycerate prepared in its turn from D-mannitol [11]. Here we report on the conversion of the latter into the C 13 -C 21 epothilone fragment (R)-(III), a promising intermediate for the epothilone synthesis through the stage of the hydroxy group substitution with the reversal of the streochemical confi guration of the atom C 15 [12] (Scheme 1).…”